The main problem with new builds is that it's not uncommon for the contractors involved (plumbers, window installers, etc) to deliver completely sub-par work, especially at the early stages of a development when things have yet to be ironed out.
Additionally, while a new build will usually carry a 10 year NHBC certificate, be very aware that you only have the first 2 years on a new build to ensure any snagging issues are sorted out - after that period, the NHBC certificate protects only against significant structural issues, ie, your house is falling down.
There are some genuinely nice new build designs out there, but do be aware that for mortgage purposes some companies will reduce the mortgagable value by 10%.
Also, negotiate when buying a new build. Builders are torn between maximising profit and shedding excess inventory. The rate of demand shows which way they are going.
Hope that helps.